The present invention relates generally to the field of industrial battery stacks, and more particularly, to industrial battery stacks wherein the positive plates have been wrapped with a semi-perforate inert material for the purpose of preserving and extending the life of these plates.
It has long been known to the art that one method of effectively positioning plates of a storage battery is to provide projections protruding from the plates which are cast therein for the purpose of spacing those plates during stacking and subsequent insertion into the storage battery case. Similar projections may also be disposed along the bottom of the battery plates for the purpose of providing "feet" which are useful in holding the bulk of the battery plate material away from a surface upon which may accumulate residues which, if allowed to contact the battery plate material, might tend to shorten the useful life of the battery. In the construction of automotive batteries, these projections which are formed along the longitudinal edges of the battery plates used in the battery stack are normally included on both the positive and negative plates. In order to avoid shorting which might be caused by buckling, these projections are often offset so that the various projections within the stack of each positive and negative plates are coaxial, but are spaced apart longitudinally by distance sufficient to minimize the likelihood of shorting between plates. One arrangement similar to that described with respect to both positive and negative plates and separators is disclosed in U.S. Pat. No. 3,294,258 entitled Apparatus for Aligning the Plates and Separators of a Battery Stack. Heretofore it has been common to stack battery plates, such as those shown in U.S. Pat. No. 3,294,258, in an alignment box in order to produce a battery stack which may then be transferred out of the alignment box for the purpose of forming battery straps and lugs thereon, either by burning, casting, or some other method known to the art.
In the stacking and burning of industrial battery plates, various difficulties have been encountered which differ substantially from those encountered in the production of battery stacks intended for automotive or other non-industrial uses. In particular, the currents produced within a typical industrial battery far exceed those normally encountered in an automotive battery, and therefore, the stresses which are encountered by the battery plates, and particularly, the positive plates, are substantially increased in the typical industrial battery. One method of improving the durability of the positive plates incorporated into an industrial battery is that of wrapping each of the positive plates with an inert wrapping film, such as polyvinyl chloride, which wrapping film is perforated in the areas over the broad faces of the positive plates, but which is inperforate in the portion of the wrapping material which overlaps the longitudinal edges of the positive plates. It has been found that by wrapping the positive plates of an industrial battery in this manner, that the likelihood of treeing and the damages which might be expected from warping or shedding are kept to a minimum. Unfortunately, the wrapping of positive battery plates in an industrial battery stack brings with it certain problems relating to the stacking and positioning of those battery plates, not only initially within the battery stack prior to burning, but also subsequently after the assembly of the battery stack into the case in terms of properly aligning the positive plates with respect to the adjacent negative plates and separators, as well as with respect to the side walls of the battery. Projections extending from the longitudinal edges of a positive battery plate are furthermore not practical, due to the fact that the wrapping of these battery plates with the above described inert material will be interfered with. Furthermore, the wrapping of the positive plates, together with the large size of those plates as normally encountered in the production of a typical industrial battery makes it very difficult to efficiently utilize a given unit volume within an industrial battery case. That is, unlike automotive batteries, industrial battery plates, due to their relatively greater size and weight, and the attendant dimensional irregularities which may be cast or formed therein during processing, prevents the typical industrial battery stack from being moved as compactly as that normally expected in the automotive battery production.